This invention is related to the logging of data obtained from cores produced by the drilling of core boreholes. The principles of the invention are particularly applicable to the evaluation of radiometric data but are equally applicable to the measurement of emissivity of practically any nature, especially under circumstances where the source of the emission is not easily localized.
In the drilling of core boreholes for exploratory and survey work in uranium mining, the resulting cores are usually evaluated visually and the visual geological and mineralogical features of sections of apparent principal interest are logged in detail. At least some of the sections of the core are split longitudinally and assayed for minerals of interest. In this process the split section of core which is used is destroyed.
The core is often assayed in sections which are approximately 10 cm long and the results are reported in terms of the milling width. The milling width is generally of the order of from 1 m to 1,5 m. The assay thus gives the average mineral content over the milling width, this data being required for an economic evaluation of the ore body, but it gives little information on the detailed grade or value distribution of the uranium over the length of the core, for example whether the reef is wide and of a low grade or narrow and of a relatively higher grade. This information may in some cases be indicated by the visual log of the core but this can be deceptive.
In many instances a detailed knowledge of the value or grade distribution over the milling width is not required for certain decisions based on economic considerations of a particular deposit but such knowledge can be of considerable value for optimum metallurgical processing, and for geologists and sedimentologists. Detailed information on the grade distribution over the milling or mining width does, however, become essential in the evaluation for any ore sorting or ore upgrading operation whether this be based on radiometric or heavy media techniques.
For example in the case of radiometric sorting of uranium bearing ores a reef which is 1 m wide and which has an average uranium content of 0.1 kg uranium per ton over the 1 m reef and milling width would not be sortable while a reef which is 10 cm wide with a uranium grade of 1 kg uranium per ton over the 10 cm reef width, but also having an average grade over the 1 m milling width of 0.1 kg uranium per ton would be eminently sortable, with over 80% of the mined ore being discarded or rejected in the sorting operation and with about 98% of the total uranium content being recovered.